How do I de-lime gas water heater? I heard there is "mag erad". But how do I use it? Where do I pour it in? My >10 year old 40G gas water heater is getting so loud my condo neighbors are complaining. I am pretty sure it is the minerals inside. I partially drain it every couple months but the noise will come back. Today I did a >90% drain but the drain is getting clogged by the mineral it was going very slow. Thanks in advance.